text: The main experimental difficulty in observing cluster decay comes from the need to identify a few rare events against a background of alpha particles. The quantities experimentally determined are the partial half life, T, and the kinetic energy of the emitted cluster E. There is also a need to identify the emitted particle.
  Detection of radiations is based on their interactions with matter, leading mainly to ionizations. Using a semiconductor telescope and conventional electronics to identify the C ions, the Rose and Jones's experiment was running for about six months in order to get 11 useful events.
  With modern magnetic spectrometers (SOLENO and Enge-split pole), at Orsay and Argonne National Laboratory (see ch. 7 in Ref. [2] pp. 188–204), a very strong source could be used, so that results were obtained in a run of few hours.
  Solid state nuclear track detectors (SSNTD) insensitive to alpha particles and magnetic spectrometers in which alpha particles are deflected by a strong magnetic field have been used to overcome this difficulty. SSNTD are cheap and handy but they need chemical etching and microscope scanning.
  A key role in experiments on cluster decay modes performed in Berkeley, Orsay, Dubna, and Milano was played by P. Buford Price, Eid Hourany, Michel Hussonnois, Svetlana Tretyakova, A. A. Ogloblin, Roberto Bonetti, and their coworkers.
  The main region of 20 emitters experimentally observed until 2010 is above Z = 86: Fr, Ra, Ac, Th, Pa, U, Pu, and Cm. Only upper limits could be detected in the following cases: C decay of Ba, N decay of Ac, O decay of Th, Ne decays of Th and of U, Mg decays of U, Mg decay of Np, and Si decay of Pu and of Am.
  Some of the cluster emitters are members of the three natural radioactive families. Others should be produced by nuclear reactions. Up to now no odd-odd emitter has been observed.
  From many decay modes with half-lives and branching ratios relative to alpha decay predicted with the analytical superasymmetric fission (ASAF) model, the following 11 have been experimentally confirmed: C, O, F, Ne, Mg, and Si. The experimental data are in good agreement with predicted values. A strong shell effect can be seen: as a rule the shortest value of the half-life is obtained when the daughter nucleus has a magic number of neutrons (N = 126) and/or protons (Z = 82).
  The known cluster emissions as of 2010 are as follows: